Studies on the effect of NAD ion analogs on the DNA repair mechanism in nuclei isolated from rat liver, HeLa cells, Novikoff hepatoma, fetal rat liver and Xeroderma pigmentosum cells would be continued. Because of our observation on the role of the 2'- and 3'-hydroxyl groups of the adenine ribose of NAD ion on DNA repair, a logical extension of these findings would be to determine if 2',3'-dideoxyNAD ion has an affect on DNA repair. Second, we will determine if 2',3'-ditritio-dideoxyNAD ion is a substrate for the ADP-ribosylation reaction. With no hydroxyl groups on the 2' and 3' positions of the 2',3'-dideoxyNAD ion, we can limit the addition of one ADP-ribose to the endonuclease. We can then ask the question, "Is the ADP-ribose polymer necessary to regulate DNA repair, or is the endonuclease inhibited with only ribose attached to the endonuclease?" We have synthesized NAD ion labeled in the ribose moiety attached to the nicotinamide ring. The oligo- and poly(ADP-ribose) will be hydrolyzed with snake venom phosphodiesterase and alkaline phosphatase. Only (3H)ribose will be covalently linked to the endonuclease. The ribosylated endonuclease will be tested for endonuclease activity. The role of NAD ion in the regulation or protein synthesis in rabbit reticulocyte lysates will also be investigated by studying the affect of NAD ion on the deacylase and the affect of NAD ion on either the alpha or beta globin chain. The biosynthesis of minimycin will be continued to further clarify how carbons 2, 3, and 4 of alpha-ketoglutarate serves as the carbon skeleton of the aglycone of the C-nucleoside antibiotic, minimycin. BIBLIOGRAPHIC REFERENCES: Suhadolnik, R.J., Lennon, M.B., Uematsu, T., Monahan, J.E., and Baur, R., "The Role of the Adenine Ring and the Adenine Ribose of Nicotinamide Adenine Dinucleotide in Binding and Catalysis with Alcohol, Lactate, and Glyceraldehyde-3-phosphate Dehydrogenases", J. Biol. Chem. 252 (1977), in press. Isono, K., and Suhadolnik, R.J., "Biosynthesis of the C-Nucleoside, Minimycin: Asymmetric Incorporation of Glutamate and Acetate into the Oxazine Ring", J. Antibiotics, in press (1977).